Capacitive switch detector addressing

ABSTRACT

An emergency alarm system peripheral, such as a hazard detector, intrusion detector, or a notification appliance, includes a base that is permanently installed on a wall or ceiling, and a head which mounts to the base. Various embodiments and methods are provided to easily and efficiently assign addresses to the peripherals in the system.

CROSS-REFERENCE TO RELATED APPLICATION

The present Application for Patent is a 35 U.S.C. 371 National Phase ofPCT Application No. PCT/US2019/029164 entitled “CAPACITIVE SWITCHDETECTOR ADDRESSING” filed on Apr. 25, 2019, which claims priority toU.S. Provisional Application 62/801,469 entitled “CAPACITIVE SWITCHDETECTOR ADDRESSING” filed Feb. 5, 2019, each assigned to the assigneehereof and hereby expressly incorporated by reference herein.

BACKGROUND

Traditionally, addressable fire alarm peripherals (such as smokesensors, heat sensors, pull stations, and notification appliances) areassigned addresses using either mechanical or electronic methods. Manysuch devices consist of a base which is typically attached to anelectrical box for permanent or semi-permanent installation. A “head”containing the sensors or annunciators (lights, sounders, etc.) can thenbe removably attached to a base for easy cleaning and/or replacement.Mechanical addressing methods include, for example, rotary switches orbinary DIP switches located in either the device head itself or itsbase. Electronic addressing methods typically require the use of aproprietary tool that connects to the device and writes an address thatthe device stores electronically in non-volatile memory.

SUMMARY

An emergency alarm system peripheral, such as a hazard detector(including but not limited to detection of smoke, heat, CO, CO₂, flame,natural gas or other toxic or noxious chemicals, pull stations),intrusion detector (including but not limited to window and doorcontacts, glass break sensors, water or water level sensors, passiveinfra-red detectors) or a notification appliance (including but notlimited to sirens, voice alerts, strobes), includes a base and a head.The base is typically mounted on a wall or ceiling, in front of anelectrical box. The head, which houses the actual sensor(s) ornotification transponder(s), is attached to the base during installationor replacement.

Most of the Description below refers to “detector heads”, but for thepurposes of this invention, “detector head” includes the transponderpart of a notification appliance device that can attach to a base.

In at least one embodiment of the invention, the base includes a bank ofnon-electrical switches, each having a metallic plate that may bemanually moved to one of two (or more) positions. The head includes abank of electrical node pairs, each pair corresponding to one of theswitches, and having a node capacitance between them. When the head is,e.g., mechanically attached to the base, each node pair is in proximityto its corresponding switch. In alternative implementations, the headmay be attached to the base via one or more magnets. In the case of atwo-position switch, the metallic plate can be placed in a firstposition in which it virtually overlaps both nodes of a node pair. In asecond position, the metallic plate may not overlap either of the nodes,or may partially overlap one of the nodes.

In the first position, there is a first capacitive value between thenodes such that the nodes are capacitively coupled such that a highfrequency signal sees a low impedance and passes through. In the secondposition, there is a second capacitive value such that the nodes are notcapacitively coupled or provide a very high impedance to the highfrequency signal. The head further comprises circuitry for determiningthe position of the metallic plate based on the amplitude of the highfrequency signal after the signal has passed (or not) through the nodepair.

In an alternative embodiment, an addressable device such as a detectorhead or base includes a Near-Field Communication (NFC) transponder forreceiving an address to be assigned to the device, the addresstransmitted from a smartphone via the smartphone's NFC transponder. Theaddress may be stored in a non-volatile memory on the device.

To help the process, the installer can make use of an app running on asmartphone or other wireless portable device. The app may present a userinterface by which a user can identify the alarm device and assign anaddress to the alarm device. When the smartphone is placed in proximityto the addressable device and the installer activates a transfer, thesmartphone may transmit the assigned address via the smartphone's (NFC)transponder to the alarm device. The communication between smartphoneand addressable device could, if desirable, contain additionalinformation as well.

Where the address is received and stored in the base, the head may haveits own NFC transponder that reads the stored address from the base. Thehead may then report the address to a fire panel.

In yet another embodiment, each switch includes a non-electricaladjustable (configurable) reflecting surface that reflects light in afirst position and that does not reflect light in a second position. Theswitch may toggle between the first position and the second position. Alight source and light detector pair may correspond to each switch suchthat when the head is mounted to the base, the light source/detectorpair is positioned opposite the switch to enable detection of thereflecting surface's position.

Another embodiment uses a label with corresponding multiple detectionzones instead of switches. Each zone may be darkened, for example, bythe installer with a marker, or not darkened. Light source/detectorpairs correspond to the zones. A darkened zone will not reflectsignificant light back to the light detector, and an undarkened zonewill. Thus the head is able to determine the whether the zone has beendarkened.

Another embodiment uses a dial having concentric darkened partial bandsor rings having different radii. Light source/detector pairs correspondto each band, and depending on the position of the dial, the pattern oflight and dark bands at the light source/detector pairs determines theaddress value. The darkened portions of the bands may be implemented asgrooves that do not reflect light from the light source to the lightdetector. Alternatively, the pattern of light and dark rings may beprinted on the dial. Multiple dials may be used to increase theavailable address space.

Another embodiment uses a dial having a reflector that reflects lightfrom a central light source to one of many light detectors locatedcircumferentially around the light source. Thus only one of the lightdetectors detects light, depending on the position of the dial.Alternatively, a single light detector may be located in the center,surrounded by plural light sources. The light sources are flashed one ata time so that when light is detected by the light detector, it can bedetermined which light source was active, and therefore the position ofthe dial can be determined.

In another embodiments, a bar code or QR code or similar having theaddress thereon may be attached to the base by the installer and read bya reader in the head.

In yet another embodiment, computer executable code for an installer appexecuting on a smartphone, may cause the smartphone to display a userinterface listing plural addresses, and for each address, a descriptivelabel with which the address is to be associated. An installer mayactivate a control button corresponding to that address, which signalsthe computer executable code to perform a scan using the smartphone'scamera to read a unique identifier on a base or head to be installed atthe location associated with the label. The smartphone app may thencommunicate the selected address and the scanned unique identifier to anexternal resource, such as a fire panel or intrusion panel. The uniqueidentifier may comprise one or more of a bar code, a QR code, or text,or other visually decipherable patterns capable of holding uniqueidentifier information. Once the address is assigned, it and optionallythe unique identifier may be stored in non-volatile memory in thedevice.

The smartphone and base (or head) may each have their own Near-FieldCommunication (NFC) transponders. When the smartphone reads andidentifies the unique identifier, the unique identifier may betransferred via NFC transmission from the smartphone to the head (orbase) stored in non-volatile memory, and then communicated to theexternal resource.

It should be noted that the term smartphone includes smartphones as wellas other electronic mobile devices such as smart pads and smartwearables.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective side view of an example of a device base in acapacitive switch embodiment.

FIG. 2 is a side view of an example of a device head in the capacitiveswitch embodiment of FIG. 1 .

FIG. 3 is an example of drawing illustrating the physical matching of ametallic plate switch for a device base and a node pair for a devicehead, when the device head is installed onto the device base in thecapacitive switch embodiment of FIGS. 1-2 .

FIG. 4 is an example of a high-level schematic drawing illustrating howthe capacitive switch embodiment of FIGS. 1-3 detects the position ofthe metallic plate.

FIG. 5A is an example of a photograph illustrating a device base with abank of switches in an optical switch embodiment, and a matching devicehead with a corresponding bank of light detection components.

FIG. 5B is an example of an outline of the device head printed circuitboard of FIG. 5A, illustrating details of the light detectioncomponents.

FIG. 5C is an example of a photograph illustrating an alternativeoptical embodiment in which a label is used in the device base insteadof physically moving parts by filling in areas of the label such thatthey do not reflect light.

FIG. 6A illustrates an example of an optical embodiment in which a dialin the detector base, rather than a bank of switches, may be used to setan address.

FIG. 6B illustrates another example of an optical implementation.

FIG. 7 illustrates an example of an optical embodiment in which a devicebase has a dial that reflects light from a central light source to oneof several light sensors located radially around the light source,depending on the dial's position.

FIG. 8A is an illustration of an example of a mobile device userinterface for an installer for a unique identifier addressingembodiment.

FIG. 8B is a photograph illustrating an example of a mobile device beingused to scan the identifier.

FIG. 9 is an illustration of an example of a mobile device userinterface for an installer for an alternative unique identifieraddressing embodiment.

FIG. 10 is an illustration of an example of a mobile device userinterface for an installer for a mobile device addressing embodiment.

DESCRIPTION

Embodiments described below employ a mechanical-only set of switches ina device base for addressing purposes.

I. Capacitive Switch Detector Addressing Solutions

In at least one embodiment, the switches are located in a device base,and each switch consists of a metallic plate slideable between twopositions. The switch itself is non-electrical; the metal plates simplyslide between positions and are strictly passive, having no energysource or electrical connections of their own, nor are they physicallyconnected to any electrical component. The detector itself has PCBtracks corresponding to each switch in the base, such that when the headis installed onto the base, each pair of tracks (nodes) is proximate acorresponding switch on the base. The position of the correspondingmetallic plate determines a capacitance between the pair of tracks (nodepairs). A corresponding circuit connected to each track detects thecapacitance of the node pair, and from that, the position of the relatedswitch.

In an embodiment, a high-frequency signal generator generates ahigh-frequency signal designed to capacitively stimulate the switch'smetallic plate, and the other circuit detects the presence of thehigh-frequency signal when coupled by the switch's metallic plate whenit is in a first position, and the absence of the high-frequency signalwhen the metallic plate is in a second position.

FIG. 1 is a perspective view of the side of the base 10 that attaches toand faces the head (described below with respect to FIG. 2 ). The baseincludes a group of switches 12. For exemplary purposes, four individualswitches 14 are shown; however one skilled in the art can see that therecould be fewer or more switches, depending on the length of the addressneeded. Of course, the switches could be used to indicate parametersother than or in addition to an address, such as a group ID, whether toenable a sounder or not, etc.

Each switch 14 includes a metallic plate 14 a-14 d which in someembodiments is movably positionable, e.g., slideable, between twopositions. For example, metallic plates 14 a, 14 c and 14 d are in afirst position, while plate 14 b is in a second position. This couldindicate, for example, that this device is to have an address 1011₂ or11₁₀. The subscript “2” indicates a base 2 number and the subscript “10”indicates a base 10 number.

FIG. 2 is a view of the side 16 of the device head 20 that attaches toand faces the base 10 (FIG. 1 ). A printed circuit board (PCB) 26 has amodulated PCB track 24 that is electronically coupled to ahigh-frequency signal generator (not shown). The modulated track mayhave extended fingers 24 a corresponding to each address switch on thebase. Separate tracks 22 corresponding to each finger are proximate butelectrically isolated from respective fingers 24 a.

Looking at both FIGS. 1 and 2 , it can be seen that electrical contacts28 lock the head 20 into the contacts 18 in the base 10, such that thehead can only be installed in one way, thus ensuring that node pair (22,24 a) on the base lies aligns with a corresponding switch 14 a.

FIG. 3 illustrates a side view of a matching switch 14 and node pair(22, 24 a) when the head 20 is installed onto the base 10. It can beseen that when the metallic plate is in the ON Position 34A, it isproximate the two nodes 22, 24, and interacts with the nodes to changethe capacitance between the nodes. When the plate is in the OFF Position34B, as shown in this example, it not proximate either node, and hasvery little if any interaction with them, such that there is little tono capacitance between the nodes 22, 24 a.

FIG. 4 is a high-level schematic illustrating the operation of anembodiment of the invention. For illustrative purposes, only one switchis discussed. A high-frequency generator (oscillator circuit) 41generates a high-frequency signal and applies the signal to a modulatedPCB track 42. That signal is coupled through a closed switch 43, ornot-coupled if it is open, to sensing PCB track 44. The high-frequencysignal, if present, is sensed by a sensing circuit 48. There is onesensing circuit per switch. Here, only one sensing circuit isillustrated. Each sensing circuit includes a sensing PCB track 44, anamplifier 45 and a rectifier 46. Each sensing PCB track is paired withan extended finger 24 a (FIG. 2 ) of the modulated PCB track, and may ormay not be capacitively coupled with the corresponding finger dependingon the position of the corresponding switch's metal plate. If the metalplate does couple the modulated PCT track with a sensing PCB track, thehigh-frequency signal will be sensed and amplified by amplifier 45. Theamplified signal is then rectified by rectifier 46. The rectifiedsignals for each of the switches are then read by a microcontroller orASIC 47 which compares the amplitude of each signal against apredetermined threshold to determine the position of the switches.

It could be envisioned that a switch might have multiple positions nearthe nodes so as to interact with the nodes according to the position,enabling different values of the detected HF signal to indicate thedifferent positions.

As an example of an installation, an installer may install the bases inan area, floor, building, or the like, and set the address switches oneach base according to a blueprint or optionally, a smartphone app,installation instruction tables, etc. The bases can then be tested forwiring continuity and ground faults. The detectors can then be installedonto the previously addressed bases, and the fire panel programmed torecognize the addressable devices.

II. Optical Switch Detector Addressing Solutions

Alternatively, a mechanical-only set of switches may be located in thedetector base; however in this solution, the switches may be white orlight-colored in one position, and black or dark-colored in the otherposition. The detector itself has light detection components (eithercompletely exposed or through a “window”) capable of detecting the lightand dark conditions, that correspond to the switches and indicate theswitch positions. Each light detection component may consist of an LEDpaired with photo-detectors positioned as a pair above a correspondingswitch.

FIG. 5A is a photograph illustrating a base 51 with a bank of switches53. It can be seen that four of the switches 52 appear dark, while theothers are light. The detector head 55 includes a circuit board 56 whichhas a bank of light detection components 57 that correspond to theswitches 53. The light detection components 57 (such as anLED/phototransistor pair, but note that an LED could be configured as areceiver in place of a phototransistor pairs; other types of opticaldetectors may also be used) are positioned to align with the switches 53when the head is installed on the base 51, as shown by dotted line 59.The switches reflect light in one position, and absorb or redirect lightin the other position, for example the four dark switches 52.

FIG. 5B is an outline of the printed circuit board 56 shown in FIG. 5A,clearly showing that each individual light detection component 58comprises an LED 58A and a photodiode 58B.

Alternatively, as FIG. 5C illustrates, a “barcode” type label could beused in the base on which the installer darkens the desired address inlieu of a physical switch, for example, by filling in a space with ablack marker. Here, the base 501 includes a label 503. It can be seenthat some of the spaces on the label have been darkened 509, whileothers 507 have not. The address selected by this configuration is00111010₂ or 58₁₀, where the dark spaces are interpreted as 0's and thelight spaces as 1's. The label can be read with the same opticalsolution (LED/phototransistor pair) as described above.

FIGS. 6A and 6B illustrate another embodiment in which a dial, ratherthan a bank of switches, may be used to set an address in the detectorbase without the base having any electronics. The address is readoptically by the detector head. Here, there are no switches; the addressdepends instead on the orientation of the dial 61 with respect to thedetector head. As shown in FIG. 6A, a dial 61 has a set of partialconcentric grooves 63, with the inner most ring representing 2⁰ and theoutermost ring representing (because there are four rings in thisexample) 2³. LED/sensor pairs 65 on the detector head (and shown here toshow how the alignment works) correspond to each groove location, anddetermine whether a groove is present or not—presence being indicated bythe shaded rings. Depending on the configuration of the dial, light froman LED 67 may be directed to a photodetector 69 to determine the “value”of a particular band. In the orientation shown, the 2³ position is theonly one that has a groove; hence the address is set to 8. FIG. 6B showsa cut-away side-view of a dial 61, illustrating the grooves in theillustrated orientation.

One skilled in the art would recognize that there could more or lessgroove rings, thus increasing or decreasing the address spacerespectively. Alternatively, or in addition, multiple dials andcorresponding LED/sensor pairs on the detector head could be used toexpand the address space. The LED and phototransistor pairs are shownfor illustrative purposes but they reside in the detector head, one pairfor each groove on the dial in the detector base 63. In the “on”position for a given radius (four grooves shown), light from thecorresponding LED is reflected back to the photodetector. In the “off”position, a switch does not reflect light to the photodetector. With theturning of the dial, the orientation of the grooves will change and adifferent address will be read. The bands may comprise grooves torepresent darkened areas as has been discussed. Alternatively, a labelmay be used that has a printed pattern similar to that shown in FIG. 6A.The light from the LED may include infra-red light, visible light,and/or ultra-violet light.

FIG. 7 illustrates yet another embodiment in which the base has a simpleradial reflector within a dial (not shown) that reflects between one ofplural radial light sensors 71 and a LED 73 in the middle. The detector71 that detects the light from the LED indicates the dial position andhence the selected address. Conversely, there could be a single lightsensor in the center and an array of light sensors distributed radiallyaround the center. By pulsing the LEDs one at a time, and sensing forwhich pulse light is detected, the dial position can be determined. Aswith all the examples described above, there are no electronics in thebase, just a rotatable dial with a reflector.

This concept provides a mechanical (easy, tool free) addressing solutionwithout incurring the cost of an additional circuit board andconnections in the base, or an even lower cost solution with the“barcode” approach.

III. Fire Alarm Peripheral Addressing Using a Smartphone

In this invention, the address of a device such as a smoke or heatdetector is stored electronically. The address can be set by using asmartphone app that sends the address wirelessly to the device usingBluetooth or Near-Field Communication (NFC).

The use of a smartphone eliminates the requirement of a proprietary toolto set the address on fire alarm system peripherals. This solution alsomakes easy to change the address of a device while it is installed. Inthe case of NFC, it allows devices to be addressed without connectingthem to anything, and in some cases without opening their packaging.

The smartphone may be used to program the base, or alternatively, adetector head. Because the NFC transceiver in the phone is used, nopower is needed in the device being programmed. This may obviate theneed for additional connectivity or communications in the device,resulting in significant cost savings. An NFC reader may be incorporatedinto the detector head so that when installed onto the base, the headuses its NFC reader to read the address from the base unit.Alternatively, the detector head could read the address from the basethrough additional electrical contacts (or through power contacts withthe base).

In an embodiment, an installer, with the aid of a building layout, maydetermine the address required for a particular device in a particularlocation, office or hallway, etc. FIG. 10 illustrates a user interfaceof a mobile device app 100 that an installer would use.

The current address to be assigned is shown at 101. In this case, theaddress is “217”. To change the address, the installer may use theincremental up and down buttons (102A and 102B respectively), or may usethe keypad 104 to directly enter an address. The incremental buttons102A, 102B are useful when assigning addresses sequentially or nearsequentially.

When the desired address is showing at 101, the installer may then holdthe mobile device close to the base and select the ADDRESS DEVICE button103. If the same address has previously been programmed into anotherdevice, the mobile device may alert the installer audibly with a beep orvoice, or a message showing on the screen, or even dimming the addressbefore the ADDRESS DEVICE button is selected.

When all of the detectors have been scanned and installed, the filecontaining the information (address and unique identifier) can betransferred to the Programmer software, which may then be used toprogram the panel.

IV. Fire Alarm Peripheral Addressing Using a Unique Identifier

FIGS. 8A and 8B illustrate an exemplary embodiment in which eachaddressable fire alarm peripheral contains a unique digital identifier(similar to a MAC address) that is assigned during production. Forexample, the unique identifier may be stored on a barcode on thedetector and in non-volatile memory.

During installation, a configuration file generated by a Programmerapplication on a PC may be installed onto a mobile/smart device, such asa smartphone, smartpad or some other mobile device capable of reading abarcode or QR code, etc. The detector bases may be installed on ceilingsor walls. After testing and correcting wiring as needed, construction atthe site may be completed. FIG. 8A illustrates a mobile app interface 80that an installer may use to register and associate an address to theunique digital identified in the detector.

In this example, the shaded rows represent devices that have alreadybeen associated with an address. For example, the second row 81represents a detector that has been labeled as “Atrium NE”. The uniqueID of that detector is 3C4A1, and that detector has been assigned toaddress “2”.

The unshaded rows represent devices that have not yet been scanned andassigned an address. For example, the sixth row 82 does not show a codeor unique ID, indicating that no detector head has been assigned to thatlocation yet. The installer, noting that a device for the location“Conference Rm” has not yet been assigned, would go to that location(Conference Rm), and press the SCAN button 83 for that row 82.

At this point a scanner will appear on the smart device, allowing theinstaller to scan the bar code on the detector head and read the uniqueidentifier embedded thereon as illustrated in FIG. 8B. The unique IDwill then appear on that line in the CODE column and is automaticallyassociated with address “6”. The installer could then repeat the processfor “Classroom” and so on. Note that each row has a SCAN button whichturns into a RESCAN button, allowing the installer to rescan a device,or later replace the installed device with another device with adifferent unique identifier. For example, in row 81, the button 84 haschanged to “RESCAN” because the address “2” has already been assigned,but if the assignment needs to be redone, for example if the installermade a mistake, the installer can press RESCAN and reassign the address.

After scanning the detector head and assigning an address to it, it canbe mounted onto the base at that location. The scanned detectorinformation (address, label, unique identifier/code) can then betransferred from the smart device back to the Programmer, which can thenbe used to program the panel. The panel may then initialize all deviceson the loop by communicating their functional address (1, 2, 3 . . . )to them using the unique identifier. The communication may be real-timeor delayed.

An installer can initiate this configuration of the fire panel from themobile device.

In an alternative installation method, a configuration file may not befirst generated by the Programmer software. Instead the installer,presented with a smart device user interface 90 as shown in FIG. 9 , mayselect or scan an address from a building plan. The installer would thengo to the location identified in the plan corresponding to the selectedaddress.

The current address to be assigned is shown at 91. In this case, theaddress is “217”. To change the address, the installer may use theincremental up and down buttons (92A and 92B respectively), or may usethe keypad 94 to directly enter an address. The incremental buttons 92A,92B are useful when assigning addresses sequentially or nearsequentially.

When the desired address is showing at 91, the installer may then selectthe SCAN DETECTOR button 93. As with the previous installation method, ascanner will appear on the smart device (refer back to FIG. 8B),allowing the installer to scan the bar code on the detector head andread the unique identifier embedded thereon. The installer may theninstall the detector onto the corresponding base.

The scanned detector information (address, label, uniqueidentifier/code) can then be transferred from the smart device back tothe Programmer, which can then be used to program the panel. The panelmay then initialize all devices on the loop by communicating theirfunctional address (1, 2, 3 . . . ) to them using the unique identifier.

An installer can initiate this configuration of the fire panel from themobile device.

In alternate embodiments, the unique identifiers could be attached tobases rather than to the detector heads. As such, no new addressingwould need to occur should a detector head need replacement.

Alternatively, a first portion of the unique identifier may be stored inthe detector head and a second portion of the unique identifier storedin the base. This could be useful if, for example, there is a desire tomaintain an association between the device and the base.

V. Auto Addressing

In yet another embodiment for assigning addresses, the bases may firstbe installed, wiring tested and construction finished. The panel isplaced into commissioning mode, and the detector heads are installed ina specific order according to a plan that indicators the order in whichthe detectors head are to be installed. Each detector, upon itsinstallation, announces itself to the panel, and the panel thenautomatically assigns the next logical address.

What is claimed is:
 1. A device comprising: a base with a non-electricalswitch comprising at least one metallic plate positionable to at least afirst position and a second position; a device head comprising at leastone pair of electrical nodes having a node capacitance between them;wherein, when the device head is attached to the base, each of the atleast one pair of electrical nodes is in proximity to a correspondingone of the at least one metallic plate; and wherein when thecorresponding metallic plate is in the first position, the nodecapacitance has a first capacitive value, and when said metallic plateis in the second position, the capacitance has a second capacitivevalue.
 2. The device of claim 1, the device head further comprisescircuitry that determines whether the node capacitance has a valuecorresponding to the first capacitive value or the second capacitivevalue.
 3. The device of claim 2, wherein the circuitry furthercomprises: a high-frequency signal generator in electronic communicationwith a first node of said node pair; and a sensor circuit in electroniccommunication with a second node of said node pair, the sensor circuitis configured to perform the steps of: sensing a high frequency signalfrom the high-frequency signal generator, determining a signal strengthof the high frequency signal, determining, based on the signal strength,the node capacitance value, and determining, based on the nodecapacitance value, whether the corresponding metallic plate is in thefirst position or the second position.
 4. The device of claim 1, whereinthe base further comprises a plurality of non-electrical switches. 5.The device of claim 4, wherein the plurality of non-electrical switchesare used to form an address for the device based on positions of theirrespective metallic plates.
 6. The device of claim 1, wherein the atleast one metallic plate is slideable between the first position and thesecond position.
 7. The device of claim 1, wherein the at least onemetallic plate is snappable into the first position or the secondposition.
 8. The device of claim 1, wherein at least one node of the atleast one pair of electrical nodes includes a printed circuit board(PCB) track.
 9. The device of claim 1, wherein the device head is adetector head including at least one environmental sensor.
 10. Thedevice of claim 9, wherein the at least one environmental sensorincludes at least one of a smoke sensor, a heat sensor, or a toxic gassensor.
 11. The device of claim 1, wherein positions include a firstposition and a second position.
 12. The device of claim 1, wherein thedevice head is a detector head including at least one intrusiondetector.
 13. The device of claim 1, wherein the intrusion detectorincludes a window contact sensor, a door contact sensor, a glass breaksensor, a water level sensor, or a passive infra-red detector.
 14. Adevice comprising: a base having a plurality of switches, each switch ofthe plurality of switches includes a corresponding metallic platepositionable between at least two positions; a device head including aplurality of pairs of electrical nodes, each pair having a nodecapacitance; wherein when the device head is mechanically attached tothe base, each pair of nodes of the plurality of pairs of electricalnodes is in proximity to a corresponding switch of the plurality ofswitches in the base; and wherein the node capacitance for each switchis dependent on a position of the corresponding metallic plate.
 15. Thedevice of claim 14, further comprises means for determining a nodecapacitance value for each pair of nodes of the plurality of pairs ofelectrical nodes.
 16. The device of claim 15, further comprises meansfor determining the position of the corresponding metallic plate of eachswitch based on the corresponding node capacitance.
 17. A devicecomprising: a base with a switch having a metallic plate positionable toa first position and a second position; a device head having a pair ofelectrical nodes, the pair of electrical nodes has a first capacitivevalue when the metallic plate is in the first position, and a secondcapacitive value when the metallic plate is in the second position;wherein when the device head is mechanically attached to the base, thepair of electrical nodes is in proximity to the switch; and the devicehead includes means for determining whether a current capacitive valuecorresponds to the first capacitive value or the second capacitivevalue.
 18. The device of claim 17, wherein the device is a hazarddetection device.
 19. The device of claim 18, wherein the hazarddetection device includes a smoke detection device, a heat detectiondevice, a carbon monoxide detection device, a carbon dioxide detectiondevice, or a natural gas detection device.
 20. The device of claim 17,wherein the device is a notification appliance.
 21. The device of claim20, wherein the notification appliance includes one or more of a siren,a voice alert system, or a strobe.